The present invention relates to a method of bonding a first, vitreous sheet to a second sheet via an intervening body of adhesive material.
In the most widely used techniques for bonding a vitreous sheet to another sheet, for example another vitreous sheet, the two sheets are assembled on either side of a film of plastic material and the assembly is degassed and subjected to firm bonding conditions. The most widely used plastic film is probably polyvinyl butyral which is readily available in sheets 0.38 mm thick. One or more such sheets may be used to provide the adhesive interlayer as desired. Other materials which are used in film form are polyvinyl chloride and polyurethane.
Whilst such bonded laminates are perfectly satisfactory for many purposes, problems have been encountered in certain particular situations where a high bonding efficiency is required. The problem arises because, over the course of time and despite the degassing step to which the assembly was subjected prior to bonding, gas bubbles can appear within the thickness of the plastics film used. Delamination can also occur. This is particularly the case where the laminate is exposed to direct solar radiation for prolonged periods.